Acoustic Emission Characteristics Of Calcareous Sand Particle And Its Aggregates Cemented By MICP

From the establishment of Sansha City to the initiative of 21st century Maritime Silk Road,there are more and more development and construction activities in the relevant area of South China Sea.Widely distributed in those areas,calcareous sand has the characteristics of irregular shape,more edges and corners,brittleness and fragility which puts higher requirements on the engineering activities based on calcareous sand.In which case microbial induced calcite precipitation?MICP?technology seems to be a feasible and environment-friendly choice,but the research on acoustic emission and failure mechanism characteristics of calcareous sand particle and its MICP-cemented aggregates wasn't so much.Based on those considerations,this paper conducted compression test on calcareous sand single particles and samples treated by MICP technology,the calcite and loose calcareous sand,and the pressure and acoustic emission signals were monitored which then were analyzed by methods of probability density statistics and maximum likelihood estimation,and the main conclusions are as follows:?1?There was a good correlation between the acoustic emission signal and the pressure signal,and it seemed feasible to monitor the state of calcareous sand by acoustic emission technology.?2?Under compression,the calcareous sand single particles,calcite,MICP-treated calcareous sand samples showed a significant feature of force drops,and the effective force drop and waiting time of that followed power law.The power law exponents for effective force drops of them were 2.04,2.01 and 1.62,respectively,while the effective waiting time power law exponents were all about 2.40.?3?The waiting time of acoustic emission signals under all test conditions of calcareous sands in this paper followed double power law,and the critical waiting time was in the range of 10^-110⁰ s,and below which the power law exponent is less than1.0 and beyond which the exponent is about 2.0,while the aftershock sequences of them followed power law with exponent about 1.0.?4?Acoustic emission energy of calcareous sand single particles,loose calcareous sands during test followed power law with exponent of 1.44 and 1.70 respectively,and the AE energy of MICP-treated calcareous sand sample also followed power law whose maximum likelihood estimation curve has a convex segment while overall the plateau segment was located between 1.44 and 1.70.?5?The maximum likelihood estimation curves of data obtained by numerical combination of different ratios of acoustic emission data of calcareous single particles to loose samples under compression,and the curves of MICP-treated calcareous sand samples and the after-peak stable segment of standard samples under compression showed a good agreement.